1. Field of the Invention
The present invention relates generally to intraocular lens implants and more specifically to a high gain implantable intraocular lens which utilizes a dual lens device to reduce capsular bag action to achieve focal point accommodation with minimal stress on ciliary muscles.
2. Background Art
The most relevant prior art appears to be disclosed in U.S. Pat. No. 5,674,282 issued on Oct. 7, 1997 to Cumming. This disclosure also relates to an accommodating intraocular lens designed to be implanted in the human eye capsular bag after the natural crystalline lens has been surgically removed such as during cataract surgery. Accommodation is the muscle-controlled change in focal point of the eye lens such as for viewing an object near the eye after initially viewing a distant object.
The lens disclosed in the Cumming patent is a relatively simple convex lens and accommodation requires movement of the lens toward and away from the retina of the eye. Unfortunately, because the gain of a simple convex lens is low, the distance the lens must be actually moved within the eye to achieve a large focal length change, is relatively large. Requiring a large distance for lens movement means that achieving accommodation for near vision is difficult at best and may ultimately become impossible when the ciliary muscles become too weak or too tired to achieve the necessary lens movement.
It would be highly advantageous if an implantable intraocular lens for ciliary muscle accommodation control, could be designed to permit large focal point variation and range of accommodation with less muscle strain. In other words, a higher gain controllable lens, which provides needed accommodation with less movement and less muscle exertion, would be an extremely desirable improvement. One prior art attempt at an implantable complex lens device to provide muscle control accommodation is disclosed in U.S. Pat. No. 5,275,623 to Sarforazi wherein two spaced convex lenses have their spacing altered by muscle control of the capsular bag. However, a dual convex lens system still requires a substantial movement to accommodate large focal point variation.
The present invention comprises a high gain lens system for implant into the capsular bag after removal of the natural crystalline lens, such as a result of cataract surgery. While the invention herein has certain characteristics in common with the prior art such as the aforementioned patents to Cumming and Sarforazi, its uniqueness resides in the achievement of a higher optical gain and greater range of accommodation which provides full focal length accommodation with less muscle exertion. A preferred embodiment of the invention comprises a combination of a positive or convex lens and a negative or concave lens. These two lenses are spaced from one another and their relative spacing and respective focal lengths determine their combined focal length. The two lenses are joined along their perimeters through a common, interface which may be either integral to or attached to the respective lenses. In the preferred embodiment, the interface is formed as a narrow, flexible joint which acts an annular pivot for controlling the spacing between the lenses. The interface extends radially from this joint along two substantially parallel planes around opposing portions of the lens structure forming a scissor-like pair of closely spaced haptic flanges on each of two opposed sides of the lenses.
When the lens system of the preferred embodiment is inserted into the capsular bag, the two opposed haptic flanges on each side, extend toward the inner radial edge of the bag adjacent the ciliary muscles. When the muscles contract, the bag is stretched thereby compressing the haptic flanges together or at least toward one another. This action cause the two lenses to separate further from each other and the increased spacing between the positive and negative lenses shortens the focal length to permit focusing of objects at near distances. On the other hand, when the muscles relax, the bag relaxes also, the haptic flanges separate and the lenses come closer together. The reduced spacing between the positive and negative lenses, increases the focal length to permit focusing of objects at far distances. Thus, the preferred embodiment permits muscle control of the focal length of the lens system. Moreover, it will be seen hereinafter that the amount of movement of the lenses relative to one another to achieve a given change in focal length is relatively small because the optical gain is high. Therefore, the invention herein constitutes a significant advance over the prior art by providing a practical lens system that permits easier and greater extent of accommodation using ciliary muscles attached to the capsular bag. A second embodiment of the invention employs the same two lenses of the first embodiment, but with a different spacing control implementation based on the same pivoting scissor technique. A third embodiment employs an enclosed ring forming a unitary pressure chamber where increased pressure separates the two lenses.
An important benefit of the lens system of all of the disclosed embodiments is the large range of focal lengths that result. Such a large range assures compensation for changing lens characteristics due to aging or infirmities such as nearsightedness.
It is therefore a principal object of the present invention to provide an implantable intraocular high gain lens having a large range adjustable focal length which can be controlled by eye muscles.
It is another object of the present invention to provide a focal length adjustable implantable intraocular lens which has a higher gain and larger range than such lenses of the prior art.
It is still another object of the invention to provide a complex adjustable lens system for implanting into the capsular bag of the human eye, the lens system having a positive lens and a negative lens and yielding a high optical gain based upon the relative spacing of the two lenses.
It is yet another object of the invention to provide a high gain, large range, accommodating implantable lens system configured for aligning a positive lens and a negative lens as they are moved axially relative to one another to alter their combined focal point.
It is yet another object of the invention to provide an implantable, adjustable lens system the focal length of which may be varied over a sufficiently large range to accommodate near and far vision requirements even with changing characteristics over the entire adult life of a user.
It is yet another object of the invention to provide an implantable adjustable lens system wherein a muscle-activated scissor-like operation assures continuous alignment of the lenses of the system regardless of the application of unbalanced forces.